Problems Magnesium

PROBLEM Magnesium hydroxide has a solubility product constant of 1.8 x 10-11 at 298 K. Write the equilibrium constant expression for this salt. What is the concentration of magnesium and hydroxide ions in a saturated... 

Green coloration, present in many vegetable oils, poses a particular problem in oil extracted from immature or damaged soybeans. Chlorophyll is the compound responsible for this defect. StmcturaHy, chlorophyll is composed of a porphyrin ring system, in which magnesium is the central metal atom, and a phytol side chain which imparts a hydrophobic character to the stmcture. Conventional bleaching clays are not as effective for removal of chlorophylls as for red pigments, and specialized acid-activated adsorbents or carbon are required. 

Formation of a gelatinous precipitate that is difficult to filter can be avoided by addition of magnesium oxide to the acid solution. In order to increase particle size it is often necessary to keep the solution hot for several hours however, this problem is avoided by heating an intimate mixture of ammonium bifluoride with magnesium carbonate to 150—400°C (11). Particles of Mgp2 similar in size to those of the magnesium carbonate are obtained. 

The FD C certified colors are all water-soluble dyes, but can be transformed into insoluble pigments known as lakes by precipitating the dyes with alurninum, calcium, or magnesium salts on a substrate of aluminum hydroxide. The lakes are useful in appHcations that require color whereas in dry form, such as cake mixes, or where water may be present and bleeding is a problem, such as food packaging. FD C Red Lake No. 3 was deHsted in Febmary... 

The solvent, magnesium, and RX can have a deleterious effect on the preparation of the Grignard reagent. Some of the problems are a homocoupled product, formation of RMg02X, and noniaitiated reaction of RX with Mg. Therefore, proper preparation and handling of each component must be carried out. 

A problem common to produced water appHcations is the tendency for oil fouling of the resin. If weak acid or chelate resins are used, a two-step regeneration process is required which uses acid to remove calcium and magnesium from the resin, foUowed by a dilute NaOH solution to convert the resin to the sodium form. 

Magnesium is essential to most plant and animal life (see Mineral NUTRIENTS). Dietary deficiency, rather than toxicity, is the more significant problem. 

A vacuum-retort process (Pidgeon process) was used during World War II for the production of magnesium and calcium. SiHcon, in the form of ferrosihcon, was used as the reducing agent instead of carbon to avoid the problem of cooling magnesium vapor in the presence of carbon dioxide ... 

In magnesium casting, sulfur dioxide is employed as an inert blanketing gas. Another foundry appHcation is as a rapid curing catalyst for furfuryl resins in cores. Surprisingly, in view of the many efforts to remove sulfur dioxide from flue gases, there are situations where sulfur dioxide is deHberately introduced. In power plants burning low sulfur coal and where particulate stack emissions are a problem, a controUed amount of sulfur dioxide injection improves particulate removal. 

Boiler Deposits. Deposition is a principal problem in the operation of steam generating equipment. The accumulation of material on boiler surfaces can cause overheating and/or corrosion. Both of these conditions frequentiy result in unscheduled downtime. Common feed-water contaminants that can form boiler deposits include calcium, magnesium, iron, copper, aluminum, siUca, and (to a lesser extent) silt and oil. Most deposits can be classified as one of two types scale that crystallized directiy onto tube surfaces or sludge deposits that precipitated elsewhere and were transported to the metal surface by the flowing water. 

One of the main problems associated with lime or lime-soda softening is the disposal of the sludge. Depending upon the ratio of calcium to magnesium removed and upon the amount of soda ash used, the sludge produced is 2.8—3.6 times the weight of the lime added. The principal methods of... 

A fuel treatment system will effeetively eliminate eorrosion as a major problem, but the ash in the fuel plus the added magnesium does eause deposits in the turbine. Intermittent operation of 100 hours or less offers no problem, sinee the eharaeter of the deposit is sueh that most of it sheds upon refiring, and no speeial eleaning is required. However, the deposit does not reaeh a steady-state value with eontinuous operation and gradually plugs the first-stage nozzle area at a rate of between 5% and 12% per 100 hours. Thus, at present, residual oil use is limited to applieations where eontinuous operation of more than 1,000 hours is not required. 

Fluoride F Few major industrial water problems Reduces dental decay Alum coagulation Magnesium Hydroxide reaction Anion exchange Membrane separation... 

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